This invention relates to ultrasonic measuring devices and a system incorporating the same for ultrasonically measuring or inspecting metal tubing having a wide variety of shapes and sizes.
Hitherto, objects to be measured or tested ultrasonically have been immersed in a body of water adjacent to one or more transducers. However, particularly in the case of large objects such as long lengths of tubing of substantial diameter, such arrangements have left much to be desired. One drawback has resided in the difficulty of maintaining precise alignment and spacing between the object being measured and the transducer. Another drawback has been the need to suppress or eliminate algae which tend to grow in the water and to prevent the formation of bubbles which result in spurious readings.
It has also been hitherto recognized that the disadvantages of completely immersing large objects in a body of water for coupling with an ultrasonic transducer can be largely minimized by maintaining a column or stream of water between the ultrasonic transducer and the part being inspected. Apparatus has been provided for inspecting and/or measuring parts ultrasonically, utilizing a column of water as the coupling medium instead of immersing all or relatively large portions of the part; but such apparatus has been found to be unsuited for the inspection and measurement of tubing to the exacting standards required to be met in the manufacture of large, precision tubes free from surface blemishes from alloys containing zirconium, columbium, tantalum or hafnium, as well as high temperature alloys and stainless steels.